Safety and time are of the essence in regaining control of a well experiencing loss of wellbore pressure control. Loss of pressure control and confinement of a well is commonly referred to as a “blowout.” Well control pressure management or “intervention” is required to regain pressure control and confine wellbore fluids within the formation and wellbore. Well control intervention is an important concern not only to the oil and gas industry from a safety and operations standpoint, but also with regard to protecting commercial, environmental, and societal interests at large.
Well control intervention systems and methods are generally classified as either conventional or unconventional. Conventional intervention systems are generally used when the well can be shut-in or otherwise contained and controlled by the wellbore hydrostatic head and/or surface pressure control equipment. In contrast, unconventional well control intervention systems are generally used to attempt to regain control of flowing wells that cannot be controlled by the wellbore fluid and/or surface pressure control equipment. Such “blowout” situation may result from failure of downhole equipment, loss of wellbore hydrostatic control, and/or failure of surface pressure-control equipment. In both intervention classifications, the object of regaining well control is to halt the flow of fluids (liquid and gas) from the wellbore, generally referred to as “killing” or “isolating” the well. Unconventional methods are more complex and challenging than conventional methods and frequently require use of multiple attempts and/or methods, often requiring substantial time investment, including sometimes drilling relief wells. Improved methods and systems for unconventional well control intervention are needed.
Unconventional well control intervention methods include “direct” intervention, referring to intervention actions occurring within the wellbore and indirect intervention refers to actions occurring at least partially outside of the flowing wellbore, such as via a relief well. Two known unconventional direct intervention methods include a momentum weighted fluid methods and dynamic weighted fluid methods. Momentum weighted fluid methods rely upon introducing a relatively high density fluid at sufficient rate and velocity, directionally oriented in opposition to the adversely flowing well stream, so as to effect a fluid collision having sufficient momentum that the kill fluid overcomes the adverse momentum of the out of control fluid stream within the wellbore. Such process is commonly referred to as “out running the well.” This is often a very difficult process, especially when performed at or near the surface of the wellbore (e.g., “top-weighted fluid”).
Dynamic weighted fluid methods are similar to momentum weighted fluid methods except dynamic weighted fluid methods rely upon introduction of the weighted fluid stream into the wellbore at a depth such that hydrostatic and hydrodynamic pressure are combined within the wellbore at the point of introduction of the weighted fluids into the wellbore, thereby exceeding the flowing pressure of the blowout fluid in the wellbore and killing the well. Dynamic weighted fluid interventions are commonly used in relief well and underground blowout operations, but are also implemented directly in wellbores that contain or are provided with a conduit for introducing the weighted fluid into the wellbore relatively deep so as to utilize both hydrostatic and hydrodynamic forces against the flowing fluid.
Need exists for a third category of well control intervention that can be relatively quickly implemented as compared to the other two intervention mechanisms, in order to interrupt the flow of wellbore fluid from the blowout until a more permanent unconventional solution can be implemented. An efficient response system of equipment and procedures is desired to provide interim well control intervention that at least temporarily impedes and perhaps even temporarily halts the uncontrolled flow of fluids from an out of control wellbore and provides a time cushion until a more permanent solution can be developed and implemented.